Getter structure



Aug. 27, 1957 w. M. COUCH, JR

GETTER STRUCTURE Filed April 28, 1954 FIG.|

INVENTOR.

WIL'LIAM M. GOUGH,JR-.

ATTORNEY llnited States Patent 2,804,564 Patented Aug. 2'7, 1957 GETTERSTRUCTURE William M. Couch, Jn, New Canaan, Conn, assignor to MaehlettLaboratories, Incorporated, Springtlale, Conn, a corporation ofConnecticut Application April 28, 1954, Serial No. 426,228

4 Claims. (Cl. 313-180) This invention relates to a novel getterstructure for us in vacuum tubes. More specifically, this inventionrelates to the physical mounting of the getter structure to avoid itsbreakage and the loss of metallic gettering particles into the envelope.

Metallic particles which are permitted to become loose within a vacuumenvelope can be the source of a great deal of difficulty. If they reachthe active electrode surfaces, they may prove contaminating to theelectrode materials or exhibit properties which are undesirable for theparticular electrode involved. Even where they do not reach theelectrodes, however, such particles may have deleterious effects. Forinstance, in high voltage tubes such as X-ray tubes and X-ray valves,such particles accumulating on an envelope portion may acquire a chargewhich in turn may result in the bombardment and puncture of theenvelope.

It has become common to employ getter wire which consists of a core ofmetallic particles of barium or other getter material within a tubularmetallic sheath. Such getter wire is commonly manufactured in longlengths or coils of wire which may be cut to suitable lengths for use ina particular tube. Where the getter wire is cut, the core of particlesis exposed. Loose particles from the ends of such getter wire haveheretofore fallen out into the vacuum envelope during the manufacture,storage or use of a tube and have proved harmful to the performance ofthe tube or shortened the life of the tube.

The present invention prevents the loss of metallic particles from theends of getter wire into the vacuum envelope. Such loss of particles isprevented by closing the ends of the getter wire. Rather than usingsoldering techniques or other techniques involving heat which mightadversely effect the later performance of the getter, the presentinvention employs a mechanical expedient which is most effective yetcannot prove harmful to the getter. This expedient is the use ofcup-like members the sidewalls of which snugly engage the ends of thegetter wire.

In the prior art the getter element has often served as its own heatingelement. Frequently the getter wire has broken before it has served allof its useful life. When the getter wire has broken, it has, of course,been impossible for it to conduct or function further as its own heater.Further activation of the getter has thus been impossible. As a resultof this getter failure, tube life has been decreased due to gassiness.Of more immediate consequence, however, has been the lose of getterparticles into the vacuum envelope out of the broken getter wire.

In the present invention a heater element is provided which is separatefrom and in addition to the getter Wire itself. This heater element isplaced in close proximity to the getter so that it will functionefficiently to cause the blowing of the getter at an appropriate time.The heater wire is advantageously composed of a refractory wire ofrelatively small diameter compared with the getter wire and isadvantageously wound in a generally helical form around the getter wire.The heater wire is much less likely to break than is the getter wireitself, despite its smaller diameter. Thus the heater wire mechanicallyreinforces the getter against breakage as well as spares the getter wirethe additional burden of acting as its own heater. Accordingly, thegetter Wire is permitted to function efficiently over the entire usefullife of the getter material which it contains.

For a better understanding of the present invention reference is made tothe following drawings:

Fig. 1 illustrates a vertical section of a portion of a vacuum envelopein the region of the stem press showing the method of mounting thegetter structure, which is shown in elevation;

Fig. 2 is an enlarged plan view from above of the getter structureillustrated in Fig. l;

of Fig. 1;

Fig. 4 illustratesin cross-section the construction of the getter wireemployed in the getter of the present invention.

Referring now to Fig. 1, it may be seen that the getter structure issupported upon a pair of lead-in Wires 10 and 11 which penetrate stempress 12. Press 12 terminates a reentrant portion 13 of a vacuumenvelope. The vacuum envelope may be of any conventional type and itsshape and size will, of course, depend upon the nature of the tube andthe size, shape and relationship of the electrodes employed therein.

Also penetrating press 12 are leads l4 and 15 which provide leading-inconnections for the filament. Outside of the vacuum envelope, leads 10,11, 14 and 15 are terminated in flexible leads 10, 11', 14 and 15',respectively.

Within the vacuum envelope leads 10 and 11 are terminated in wide spacedparallel portions. Extending between these parallel portions of leads 10and 11 is a getter wire 20. The getter wire 20 is entwined with a heaterwire 21 of refractory metal which follows a general helical path aroundthe getter wire 20. Enclosing the ends of getter wire 20 are cup-likemembers 22 and 23 which advantageously are composed of pieces of nickeltubing closed at one end by squeezing together and sealed by welding.Actually the cups are made sufficiently large to enclose several turnsof the heater wire. The snug engagement of the heater wire which is inturn wrapped tightly about the getter wire, prevents the loss of getterparticles from cups 22 and 23.

In addition to enclosing the ends of getter wire 29, cup-like members 22and 23 serve as conductors. As conductors their snug engagement ofheater wire 21 mechanically provides good electrical contact between theheater wire 21 and its enclosing cup. Since the getter wire ispreferably arranged in a semicircular pattern as shown, it is possibleto complete the electrical path through the heater wire by welding Wire10 to cup 23 and wire 11 to cup 22. It will be noted from Fig. 2 that inthe semi-circular pattern shown, the respective cup members are fixed tothe outside of lead supports 10 and 11. U-shaped baffle member 24 isarranged with its side walls parallel with the longitudinal axis of cups22 and 23 and the parallel portions of leads 11 and 12. The bottom ofU-shaped baffle member 24 is arranged parallel to the diameter of thesemi-circle formed by getter wire 20 and parallel to the parallelportions of the supports 10 and 11. Baflle member 24 is supported andheld in place by welding it to cup-like member 22. It should be notedthat cup-like member 23 is definitely out of contact with bafiie member24.

Fig. 3 is a side elevational view of the getter structure Referring toFig. 4 the cross-section of a preferred getter wire construction isillustrated. In this instance, the getter wire is composed of a core 30of granular or powdered getter material, such as barium or itscompounds, and a nickel sheath 31. One wall 31a of nickel sheath 31 isweakened by thinning it down. When a getter wire such as wire 20 is cut,loose particles from 'the getter core 30 are exposed and subject to lossout of the ends of the getter wire. Not only is this getter materiallost and hence useless as far as getter purposes are concerned, itfrequently becomes distributed. In its distributed form it may be acontaminant, free in the vacuum envelope to settle on the activeelectrodes and disturb tube characteristics. Use of snug fitting cups 22and 23 prevents loss of gettering material into the vacuum envelope.These cup members 22 and 23 may be made of nickel tubing or the likewhich is highly conductive and easily welded to support conductors and11 and baffle member 24. Likewise, nickel is capable of making goodelectrical contact with the wire, whether or not it is welded to heaterwire 21.

In order to activate the getter of this invention it is necessary toapply a voltage between flexible leads 10' and 11 so that a current mayhave a path, for instance, through leads 10' and 10 to cup 23; throughheater element 21 to cup 22; and thence back through conductor 11 and toflexible lead 11. When a current is applied to heater element 21 theresulting heat will cause the getter, particularly if it is barium, torupture the thin wall 31a of nickel sheath 31. Preferably this thin wallfaces bafile member 24, so that when the getter is fired or blown themetallic barium will be deposited on the baffle instead of on some otherless desirable area within the vacuum envelope.

With this structure the getter wire may be heated again and again,whereas when the getter wire is itself used as the conductor, it mayeasily break from repeated heating or mechanical shock. The refractoryheater wire is strong, and the vaporization of the barium will notaffect its inherent strength and other physical qualities.

It is, of course, possible to use a getter of the present invention in ashape other than that illustrated. For instance, it can be arranged in astraight line or in an S-shape or in any other convenient shape. In theevent that the shape is modified, it may be necessary to employ adifferent type of baffle structure, or arrange the getter in anotherlocation so that the getter material as it is blown will not interferewith the tubes functioning.

Although as previously explained it is not desirable to do so, it ispossible in the practice of this invention to use the getter wire as itsown heater, and thus eliminate heater element 21. Likewise, it ispossible to eliminate cup members 22 and 23 and just use a getterelement with a helical heater winding wrapped thereabout.

Many other modifications of the present invention will occur to thoseskilled in the art. All such modifications within the terms of theclaims are intended to be within the scope of spirit of the presentinvention.

I claim:

1. A getter structure for use within a vacuum envelope comprising a wireembodying an imperforate sheath enclosing a supply of getteringmaterial, the sheath having a wall portion thinned down to weaken it,cup-like members enclosing the ends of said Wire, a refractory metalheater element wire wrapped generally helically around the wire, leadsconnected to the heater element wire, through which leads a current maybe applied to said heater element, and a shield opposite the weakenedwall portion of the sheath for accumulation of gettering materialthereon upon rupture of the weakened wall.

2. A getter structure for use within a vacuum envelope comprising agetter wire embodying an imperforate sheath enclosing a supply ofgettering material, the sheath having a wall portion thinned down toweaken it, cup-like members enclosing the ends of said wire, a heaterelement wire wrapped around the sheath, leads connected to therespective ends of the heater element wire, through which leads acurrent may be applied to the heater element wire, and a substantiallyU-shaped shield opposite the weakened wall of the sheath, the getterwire being formed to a generally semi-circular pattern and beingdisposed in a plane substantially perpendicular to the bottom of theshield and with its diameter substantially parallel to the bottom of theshield.

3. A gettering device for use within the envelope of a vacuum tube, thedevice comprising a substantially U- shaped holder mounted in theenvelope, a getter wire mounted within the holder and carrying a heaterelement,

the getter wire embodying a supply of gettering material enclosed by animperforate metal sheath having a substantially thin wall portion, andleads connected to the heater element through which current may beapplied to heat the heater element and consequently heat the getteringmaterial, the thin wall portion of the sheath being directed toward thebottom of the holder whereby upon rupture of the thin wall portion byheated gettering material the holder will collect thereupon getteringmaterial escaping from the sheath.

4. A gettering device for use within the envelope of a vacuum tube, thedevice comprising a holder mounted in the envelope and embodying arelatively flat baflle portion having parallel end portions disposed atsubstantially right angles to the bafile portion forming a U-shapedstructure, a getter wire mounted on the holder and comprising a supplyof gettering material enclosed by an imperforate metal sheath have athin wall portion directed toward the baffle portion of the holder,metal cuplike members mounted on the ends of the getter wire with one ofthe cuplike members connected to one of the end portions of the holdersupporting the getter wire in position of use, a heater wire encirclingthe getter wire, and leads connected to the ends of the heater wirewhereby current may be applied to heat the heater wire and cause thegettering material to rupture the thin wall of the sheath and bedeposited on the baffle portion of the holder.

References Cited in the file of this patent UNITED STATES PATENTS286,916 Fitz Gerald Oct. 16, 1883 1,712,370 White May 7, 1929 2,273,637Glover Feb. 17, 1942 2,528,547 Reilly et al. Nov. 7, 1950 2,657,452Veenemans et a1. Nov. 3, 1953

